Semiconductors typically use metallic bond pads to make electrical connection to underlying circuitry. A metal of choice for bond pads has been and continues to be aluminum because of its reliable deposition and patterning properties. However, aluminum has relatively high resistivity as compared with other metals such as copper. However, bare copper bond pads are known to be susceptible to corrosion and generally not consistent with wiring processes such as traditional wirebonding. Copper bond pads with an aluminum cap have been proposed to overcome such difficulties. Alternatives to using such copper bond pads with coatings is to form bond pads from two or more metals, such as aluminum, gold, nickel, palladium and alloys thereof. Many wire bond structures however will not pass high temperature reliability tests. For example many conventional wire bond structures when subjected to temperatures such as 150 degrees Celsius and above for several hundred hours will exhibit failures such as interfacial voiding and physical separation from underlying connected circuitry. High temperature environments often exist in integrated circuit applications for automotive applications and extended reliability in such applications is crucial. A source of such failures is due to the intermetallic reactions which occur at the boundary of differing metals within a bond pad. The intermetallic compounds which naturally form at an interface between differing metals continue to form in response to a high temperature ambient. Thus, over time, regions of intermetallic compounds in a bond pad will propagate. These regions represent areas in which voids are formed. As voids in the bond pad structure increase in number, the bond pad structure is susceptible to separating from an underlying pad connection to create an electrical failure. Thus there is a need for an improved bond pad that is compact in size and which is reliable for extended years when exposed to a high temperature.
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